A de Laval nozzle for creation of a supersonic flow by passing a working medium through a converging-diverging channel under action of longitudinal pressure drop between the channel inlet and outlet is known; for example solid-propellant rocket engines. A de Laval nozzle is characterized by inlet and outlet sections that are respectively converging and diverging in the direction of the medium flow, between which a minimal cross-section is located.
However, the de Laval nozzle does not allow an efficient conversion of pressure energy into kinetic energy of the media stream, particularly in the event that a liquid is fed to the inlet of the supersonic nozzle and a two-phase medium is formed during its boiling due to the pressure drop inside of the nozzle below the saturation pressure.
A supersonic nozzle for boiling liquid is described in RU 2420674. This nozzles incorporates an inlet converging and an outlet diverging along the media flow sections. The minimum section of the nozzle is located between the inlet and the outlet, and the initial part of the diverging section of the nozzle has the shape of a concave curve towards the axis of the nozzle, and in the section of the nozzle where the flow velocity is equal to the local sound velocity, the curve smoothly changes to the convex curve towards the axis of the nozzle.